Lightning occurs when static electricity builds up in thunderclouds and the landscape beneath them.

Make Lightning!

The purpose of this experiment is to observe lightning formation.

Styrofoam plate

Thumbtack

Pencil with new eraser

Aluminum pie pan

Small piece of wool fabric

1. Push the thumbtack through the center of the aluminum pie pan from the bottom.

2.Push the eraser end of the pencil into the thumbtack. (The pencil becomes a handle to lift the pan.)

3. Put the styrofoam plate upside-down on a table. Rub the underside of the plate with the wool for one minute. Rub hard and fast like these kids are doing...

(Click
on a photo to enlarge it.)

4. Pick up the pie pan using the pencil "handle, " and place it on top of the upside-down plate.

...like
this...(Click
on the photo to enlarge it.)

5.
Touch the pie pan with your finger. If you don't feel anything when
you touch the pan, try rubbing the plate again.

(Click
on the photo to enlarge it.)

Try turning the lights out before touching the pan. Do you see anything when you touch the pan?

Watch this video clip (you'll need a player that plays mpeg video, like Microsoft ActionMovie) and listen to the excitement after the lights are turned out! The camera doesn't pick up the spark, but the kids sure do!

For extra excitement, get a neon tube (Neon Gas Spectrum Tube, catalog item #60910, available for about $20 from Edmund Scientific, among other places). Hold the neon tube with one hand keeping a finger over one of the ends. Touch the other end to the pie plate.

(Just for fun, check this out. . . )

What happened when you touched the metal pie pan?

What caused that?

How do you think this experiment relates to the formation of lightning?

It's all about static electricity! Lightning happens when the negative charges (electrons) in the bottom of the cloud (and your finger) are attracted to the positive charges (protons) in the ground (and the pie pan). The resulting spark is like a mini-bolt of lightning.

The accumulation of electric charges has to be great enough to overcome the insulating properties of air. When this happens, a stream of negative charges pours down towards a high point where positive charges have clustered due to the pull of the thunderhead.

The connection is made and the protons rush up to meet the electrons. It is at that point that we see lightning. A bolt of lightning heats the air along its path causing it to expand rapidly. Thunder is the sound caused by rapidly expanding air.